In the early part of the sleeping-sickness stage patients often
sleep more than usual, but later do not sleep excessively. They
become lethargic and indifferent to their surroundings, however,
and often lie with their eyes closed. When spoken to they hear
and understand what is said to them and after a longer or shorter
interval give a very brief reply.
The leucocytosis that occurs during the course of this form of trypanosomiasis is due, apparently, to secondary or terminal bacterial infections so frequently associated with the disease in its later stages. The first stage of the disease, that of fever, may last for several years; the second or nervous stage with tremors, &c., for from four to eight months. It is quite exceptional for the disease to be prolonged for more than a year from the time that the nervous symptoms become manifest, though a European who contracted trypanosomiasis in Uganda, having delusions and becoming drowsy within the year, did not die of sleeping sickness until more than eighteen months from the onset of the nervous symptoms.
The Glossina palpalis is not found in swamps. It affects a belt of from ten to thirty yards broad along banks bounding water shaded by scrub and Underwood. It may, however, follow or be carried by the animal or human subject it is attacking for a distance of, say, three hundred yards, but unless carried it will not cross an artificial clearing of more than thirty yards made in the natural fly belt. The authorities in the plague-stricken areas recommend, therefore, the clearance of belts thirty yards in width along portions of the lake side, at fords and in such other places as are frequented by natives. No infected person should be allowed to enter a “fly area,” so that they may not act as centres from which the flies, acting as carriers, may convey infection. The provision of clothing for natives who are compelled to work in fly areas is an important precautionary measure.
There seems to be some doubt as to whether Trypanosoma gambiense of Dutton is the same organism and produces the same conditions as the Trypanosoma of Bruce and Nabarro from Uganda, but most observers seem to think that the two species are the same and yield the same results when inoculated into animals. It is supposed that this trypanosome may pass through certain stages of metamorphosis in the human or animal body, and different drugs have been recommended as trypanocides during these various stages, an arsenic preparation (atoxyl) first being given, and then, when the organisms have disappeared, injections of bichloride of mercury, this salt appearing to prevent the relapses which occur when atoxyl only is given over a prolonged period. Ehrlich, treating animals suffering from trypanosomiasis with parafuchsin, found that although the parasites disappeared from the blood they soon recurred. On the exhibition of another dose of parafuchsin they again disappeared. This was repeated for a considerable number of times, but after a time the parafuchsin lost its effect, the trypanosome having acquired an immunity against this substance; they had in fact become “fuchsin-fast.” Such fuchsin-fast organisms injected into animals still retain their immunity against parafuchsin and may transmit it through more than 100 generations. Nevertheless, they cannot withstand the action of other trypanocidal drugs. The outcome of all this is that large doses of the trypanocidal drug should be given at once, and that the same drug should never be given over too long a period, a fresh drug often being effective even when the first drug has lost action.
II.—To other Animal Parasites
Filariasis.—Since Bancroft and Manson first described Filaria nocturna and its relation to the common form of filariasis, the most important contribution to our knowledge has been made, at the suggestion of the younger Bancroft, by Dr G. C. Low, who has demonstrated that the embryos of the filaria may be found in the proboscis of the mosquito (Culex ciliaris), whence they probably find their way into the circulating blood of the human subject. It appears that the filaria embryo after being taken, with the blood of the patient, into the stomach of the mosquito, loses its sheath; after which, leaving the stomach, it passes into the thoracic muscles of its intermediate host, and becomes more fully developed, increasing considerably in size and attaining a mouth, an alimentary canal, and the characteristic trilobed caudal appendage. It now leaves the thoracic muscles, and, passing towards the head, makes its way “into the loose cellular tissue which abounds in the prothorax in the neighbourhood of the salivary glands.” Most of them then “pass along the neck, enter the lower part of the head,” whence they may pass into the proboscis. Although it has never been demonstrated that the filaria is directly inoculated into the human subject from the proboscis of the mosquito, it seems impossible to doubt that when the mosquito “strikes,” the filaria makes its way into the circulation directly from the proboscis. It is important to note that the mosquito, when fed on banana pulp, does not eject the filaria from its proboscis. This, however, is not to be wondered at, as the filaria is apparently unable to live on the juices of the banana; moreover, the consistence of the banana is very different from that of the human skin. The importance of this observation, as affording an additional reason for taking measures to get rid of the mosquito in districts in which filariasis is rife, can scarcely be over-estimated.
C.—Infective Diseases in which an Organism has been found,
but has not finally been connected with the Disease.
Hydrophobia is usually contracted by man through inoculation of an abraded surface with the saliva of an animal affected with rabies—through the bite of a dog, the animal in which the so-called rabies of the streets occurs. The puppy is specially dangerous, as, although it may be suffering from rabies when the saliva contains an extremely exalted virus, the animal may exhibit no signs of the disease almost up to the time of its death. The other animals that may be affected “naturally” are wolves, cats, foxes, horses, cows and deer; but all warm-blooded animals may be successfully inoculated with the disease. The principal changes met with are found in the nervous system, and include distension of the perivascular lymphatic sheaths, congestion and oedema of the brain and spinal cord and of the meninges. Hæmorrhages occur into the cerebral ventricles of the brain, especially in the floor of the fourth, and on the surface and in the substance of the medulla oblongata, and the spinal cord.
In addition to these small haemorrhages, collections of leucocytes are met with in hyperaemic areas in the medulla oblongata and pons, sometimes in the cortical cerebral tissue and in the spinal cord, in the perivascular lymphatics of the grey matter of the anterior horns and in the white matter of the postero-internal and postero-external columns. Here also the nerve cells are seen to be vacuolated, hyaline and granular, and often pigmented; thrombi may be present in some of the smaller vessels, and the collections of leucocytes may be so prominent, especially in the medulla, that they have been described as miliary abscesses. Haemorrhages are also common in the various mucous and serous membranes; hyaline changes in and around the walls of blood-vessels; proliferation of the endothelium; swelling and vacuolation of nerve cells; pericellular infiltration with leucocytes, and infiltration of the salivary glands with leucocytes (Coats). An increased number of leucocytes and microcytes in the blood has also been made out. The virus, whatever it may be, has a power of multiplying in the tissues, and of producing a toxic substance which, as in the case of tetanus toxin, appears to act specially on the central nervous system.
In recent years fresh interest has been aroused in the morbid histology of the brain and cord in hydrophobia by the appearance of Negri’s description of “bodies” which he claims are found in the central nervous system only in hydrophobia or rabies (see Plate I., fig. 3). These bodies, which are rounded, oval, triangular, or slightly spindle- or sausage-shaped, when specially stained consist of a red (acidophile) basis in which stand out small blue (basophile) granules, rods and circles, often situated within vacuoles. A small central point which is surrounded by no clear space is supposed to correspond to the nucleus of a protozoan. But this can be little more than a suggestion. The Negri bodies are certainly present in the central nervous system in cases of hydrophobia, and have not been found in similar positions in any other disease. They are present in large numbers, even at an early stage of the disease, although they are then so small that they may easily escape detection, so small indeed that they may pass through the pores of a Berkefeld
